1. Field of the Invention
The present invention relates to a system for delivering an optical beam from a beam source to a device for using the beam, and, more particularly, to a system for either providing a beam of higher power or of a different size.
2. Description of the Prior Art
There are many commercial systems which use a beam of light in the operation of the system. Such systems include optical communication systems, optical printing systems and optical memory devices for computers. The optical source generally used in these systems is a semiconductor laser diode. Such laser diodes are small and provide a beam of relatively collimated light. However, a problem with such laser diodes is that they are limited in the power of the light beam that they emit. Making the laser diode larger so as to emit a higher power beam has the problem that the beam of light is also larger in diameter. This can be a problem when the device into which the beam is being directed is small in diameter, such as an optical fiber, because the larger laser diodes tend to lase with multiple transverse modes, whose outputs are not readily focused to small diameters. Attempts have been made to increase the power of the beam provided by using a plurality of laser diodes and through optical devices, such as lenses, compress the plurality of beams into a single beam having the power of the combined beams. However, using standard optical devices, such as lenses, etc., it has not been possible to achieve a single beam of small diameter. If the beams from a plurality of spaced laser diodes are directed through a single lens, the beams will pass through different portions of the lens which causes the beams to go in different directions. The lens may form each beam at a fine point at the image plane of the system, but the beams will be spaced apart. The beams will cross each other at the focal plane of the lens to form a single spot, but the spot formed is large in diameter at the focal plane. Thus, a small diameter combined beam is not achieved by the single lens. Also, there are times when it is desired to expand or compress the size of a plurality of beams emitted by a plurality of light sources without expanding or compressing the beam diameters by a similar amount. This has been found difficult to do with standard optical devices.